Field of the Invention
The present invention relates to a head-mounted type image display system comprising a head-mounted type image display apparatus including first and second image display devices for displaying first and second images and projection optical systems for projecting the thus displayed first and second images onto retinas of right and left eyes of a user as virtual images, and a mounting means for mounting said head-mounted type image display apparatus on the head of the user.
There have been known various head-mounted type image display apparatuses, in which images displayed on first and second image display devices such as liquid crystal display devices (LCD) are projected onto retinas of right and left eyes of a user by means of first and second projecting optical systems, respectively. The projection optical system is usually formed by lens system or concave mirror. Some of these apparatuses are called a face-mounted type or goggle type image display apparatus and some of them are termed as a helmet-type image display apparatus. In the present specification, all of these types are called a head-mounted type image display apparatus. In the head-mounted type image display apparatus, the user can see a large size image while the user is not required to hold the apparatus in position by his or her hand.
FIGS. 1A and 1B show a known head-mounted type image display apparatus disclosed in Japanese Patent Application Laid-open Publication Kokai Hei 2-281891 (prior art publication No. 1). The head-mounted type image display apparatus 150 is mounted on a head 151 of a user as illustrated in FIG. 1A. FIG. 1B is a front view of the head-mounted image display apparatus 150.
The head-mounted type image display apparatus 150 comprises a plurality of back lights 152, two liquid crystal image display devices 153 and two projection lenses 154 for projecting images displayed on the liquid crystal image display devices onto respective retinas of right and left eyes of a user. In this manner, the user can see enlarged virtual images.
In this known head-mounted type image display apparatus, when the head of the user is moved, a displayed seen might be perceived by the user differently from a seen before the movement of the head. So that the user has unusual feeling. In order to mitigate such a drawback, in Japanese Patent Application Laid-open Publications Kokai Hei Nos. 3-56923 and 4-354275 (prior art publications Nos. 2 and 3), there has been proposed a head-mounted type image display system, in which an angular movement of the head of the user is detected and a camera picking up a seen to be displayed is controlled in accordance with a detected movement of the head. In Japanese Utility Model Application Laid-open Publication Kokai Hei No. 3-80384 (prior art publication No. 4) and Japanese Patent Application Laid-open Publications Kokai Hei Nos. 5-241539 and 5-241540 (prior art publications 5 and 6), there has been proposed another known head-mounted type image display system, in which an image signal is converted in accordance with a three-dimensional movement of the head, i.e. up and down, right and left, and back and forth movements of the user's head such that the displayed image is moved in correspondence with the movement of the user's head.
In the above mentioned prior art publications Nos. 2 and 3, only the angular movement of the head of the use is considered and the three-dimensional movement of the head is not considered. In the prior art publications Nos. 4, 5 and 6, there has been disclosed how to convert the image signal in accordance with the three-dimensional movement of the head of the user, but a preferable amount of the displayed image and any correction in accordance with an amount of the movement for displaying a desired image have not been disclosed.
In the above mentioned prior art publications Nos. 5 and 6, there is described as follows: in case of displaying a computer graphic landscape image superimposed on a landscape image seen by the naked eyes of the use with the aid of a half mirrors when the user moves his or her head, the landscape image seen by the naked eyes is also changed or moved. Therefore, it is convenient to change or move the computer graphic image in accordance with the movement of the head of the user. However, the prior art publications do not disclose any concrete construction and operation for realizing the above described conception.
In the known head-mounted type image display apparatuses described in the prior art publications Nos. 5 and 6, a position at which the virtual image seen by the user is formed is determined by a mutual positional relationship between the image display device and the projection optical system, but a positional relationship between the position of the virtual image and the user's eye is fixed. Therefore, when the head of the user is moved, a position of a frame in which the virtual image is formed is moved together with the head of the user, but the virtual image is moved so that the feeling of the virtual reality is decreased. Moreover, when the head of the user is moved back and forth, a magnification of the displayed image is changed accordingly, and thus a diopter of the user is not changed when the user moves back and forth. Therefore, it could not be attained a stereoscopic effect which requires a change in diopter and optical angle.